The present invention relates generally to electric vehicle charging systems, and more particularly, to an improved system for controlling charging power in electric vehicle charging systems.
The assignee of the present invention designs and develops electric vehicle charging systems. An inexpensive and simple way to charge an electric vehicle battery at high power is to parallel several resonant chargers. Unfortunately, as more and more chargers are connected in parallel, the output power per stage drops considerably. It has been determined that this effect can be neutralized by adding distributed fourth element capacitors to each charger stage using the principles of the present invention.
Three element resonant chargers have been used in the past. Such three element resonant chargers have the following limitations. The three element resonant chargers cannot throttle down to zero power as is required in a trickle charge mode. The three element resonant chargers do not provide a voltage boosting effect. The three element resonant chargers lose a lot of power capability when stages are parallelled.
Four element chargers have been used in the past. Such four element chargers can throttle down to zero power, but they also lose power when stages are connected in parallel. The present invention provides for a solution to this problem.
It would therefore be desirable to have an improved system for controlling charging power in electric vehicle charging systems.